Final answer:
In Labrador retrievers, the presence of one gene affects the expression of another gene in determining coat color, which is an example of epistasis. Epistasis occurs when the expression of one gene masks or modifies the expression of another gene, as seen with genes E and B in labs, and also with coat color in mice and human traits like eye color and skin color.
Step-by-step explanation:
The presence of one gene in Labrador retrievers influencing coat color by affecting the expression of another gene is an example of epistasis. In Labrador retrievers, two alleles, E and B, control fur color. If a dog has the ee_ genotype, it will be a yellow lab, while B_E_ dogs are black labs, and bbE_ dogs are chocolate labs. The term epistasis refers to a situation in which the expression of one gene (E) masks or modifies the expression of another gene (B).
An analogy to this phenomenon in mice involves the agouti and pigment production genes, where mice with a recessive c allele are albino due to the C gene being epistatic to the A gene. This interaction shows how multiple genes can influence a single characteristic, something which is also true for human traits like skin color and eye color, where multiple genes have a combined effect. This complex interaction between genes, where one gene can substantially alter the expression of another, underscores the multifaceted nature of genetic inheritance.